The functions predicate->char-set and char-set-invert[!] can take a
long time if you define char-sets on a Unicode system (which you can do
on Gambit-C), especially if you follow the suggestion in the body of
the proposal:

"Large" character types, such as Unicode, should use a sparse representation,
taking care that the Latin-1 subset continues to be represented with a
dense 32-byte bit set.

So, are these really necessary?  Should we omit them?

Brad